#include <iostream>
#define PI 3.14
using namespace std;
class Circle
{
public:
	int m_r;
	double FindPrimeter()
	{
		return 2 * PI * m_r;
	}
};
int main()
{
	Circle circle;
	circle.m_r = 10;
	cout << circle.FindPrimeter() << endl;
	system("pause");
	return 0;
}